1. Field of the Invention
The present invention relates to a process for producing a decorated article. In particular, the present invention relates to a process for producing a decorated article in which the surface of a base material which is formed by injection molding or the like is laminated with a thermoplastic resin sheet.
2. Description of Related Art
Processes for producing overlay boards in which the surface thereof is laminated with a resin sheet or film have been hitherto proposed. For example, Japanese Patent Application, Second Publication (Kokoku), Sho 63-26699, discloses a process in which a thermoplastic resin film is put on the surface of a sliced veneer overlay board. According to this process, a hot-melt resin sheet having a melting point lower than that of the thermoplastic resin film is polymerized on the surface of a sliced veneer overlay board, and thereafter, the thermoplastic resin film is polymerized on the surface of the hot-melt resin sheet and pressuring is carried out at a predetermined temperature.
The above-mentioned proposed process has advantages in that a wood grain pattern is raised to the surface of the thermoplastic resin film while the thermoplastic resin film protects the sliced veneer overlay board from being soiled or the like.
However, the above process for producing an overlay board has a disadvantage in that the hot-melt resin sheet penetrates the sliced veneer overlay board, darkening the sliced veneer overlay board. Moreover, in a thermal cycle test (heat resistance test), it was discovered that delamination of the thermoplastic resin film occurs at 80xc2x0 C., which limits the applicable range of this process. In addition, this process exhibited its defects in a dry-wet test (weathering test), according to which at a temperature of 50xc2x0 C. and at a humidity of 95% RH, the appearance of the overlay board could not be maintained, as darkening in the surface worsens and dullness expands in some areas.
In addition, a conventional process for coating an injection molded article requires a great amount of time and incurs a high cost for carrying out the coating with a polyester, filling, sanding, and the like after primary molding. Moreover, this process has disadvantages in that it incurs an enormous cost for equipment to deal with environmental pollution which may be caused by the coating, which substantially increases production costs.
The present invention has been conceived taking the above disadvantages of the conventional arts into consideration; thus, the object of the present invention is to provide a process which makes it possible to manufacture a decorated article within a short time with simple equipment and which improves the heat resistance and the weather resistance of the decorated article, as well as the process to avoid penetration of glue into a base material, a surface of which is composed of an overlay, while maintaining a uniform color tone of the overlay.
In order to achieve the above object, the process for producing a decorated article according to the present invention employs a method in which a base material, a surface of which is composed of an overlay, is prepared by injection molding or the like, the overlay having a wood material layer, a first side of the wood material layer constituting a surface of the overlay; thereafter, a coloring layer is provided on the first side of the wood material layer; and the surface of the coloring layer is laminated with a thermoplastic resin sheet, and hot-pressing is carried out. In this process, a glue may be laid between the coloring layer and the thermoplastic resin sheet. A method in which a primer is additionally laid between the glue and the thermoplastic resin sheet is also applicable.
Moreover, the process for producing a decorated article according to the present invention may also employ a method in which a base material, a surface of which is composed of an overlay, is prepared by injection molding or the like, the overlay having a wood material layer, a first side of the wood material layer constituting a surface of the overlay; thereafter, the first side of the wood material layer being laminated with at least one coloring layer, which is formed by applying a colored thermosetting resin, and a sealing layer, which is composed of a colored or transparent thermosetting coating film, in that order; and the surface of the sealing layer is laminated with a transparent thermoplastic resin sheet, and hot-pressing is carried out. In this process, a glue may be laid between the sealing layer and the thermoplastic resin sheet. A method in which a primer is additionally laid between the glue and the thermoplastic resin sheet is also applicable.
The above-mentioned base material may be formed by: preparing the wood material layer; providing a metal layer on a second side of the wood material layer in a manner such that the second side of the wood material layer adheres to a first side of the metal layer; and providing a core material of the base material on a second side of the metal layer, the second side of the metal layer being opposite to the first side of the metal layer.
The above-mentioned coloring layer may be formed by applying a colored thermosetting resin containing at least one thermosetting resin, or a modified resin thereof, selected from the group consisting of urethane resins, epoxy resins, acrylic resins, and amino-alkyd resins, or by applying dye of pigment.
The above-mentioned sealing layer may be formed by applying a thermosetting resin containing at least one resin selected from the group consisting of urethane resins, epoxy resins, amino-alkyd resins, acrylic silicone resins, ultra-violet-cured urethane acrylate resins, ultra-violet-cured epoxy acrylate resins, ultra-violet-cured polyester acrylate resins, and ultra-violet-cured unsaturated polyester resins. The sealing layer may be colored or transparent.
As the above-mentioned thermoplastic resin sheet, a sheet containing at least one thermoplastic resin selected from the group consisting of fluorocarbon resins, acrylic resins, vinyl chloride resins, polycarbonate (PC) resins, acrylonitrile-butadiene-styrene (ABS) resins, acrylonitrile-styrene (AS) resins, polystyrene (PS) resins, polyethylene (PE) resins, and polypropylene (PP) resins may be employed.
According to the present invention, the formation of a thermosetting coloring layer on an overlay in a base material prevents the glue provided on the surface of the thermosetting coloring layer from penetrating into the overlay. Accordingly, a uniform wet appearance of the overlay is visible through the thermoplastic resin sheet which constitutes a surface layer in the end product while the heat resistance and the weather resistance are improved. In the case when a method in which a primer is laid between the glue and the thermoplastic resin sheet is employed, the thermoplastic resin sheet can be securely adhered.
In addition, in the case where a thermosetting coloring layer is formed with a lamination containing a coloring layer and a sealing layer in that order, the multi-layer structure of the coloring layer and sealing layer prevents the glue from penetrating even more effectively, and thus an even more uniform color tone of the colored overlay can be obtained. In addition, exudation of colorant from the coloring layer formed under the sealing layer can be prevented, as well as exudation of wood resin or the like contained in the wood material layer. Moreover, delamination of the thermoplastic resin sheet is prevented since residual functional groups (for example, isocyanate group xe2x80x94NCO in the case when a polyurethane resin is employed) in the thermosetting resin employed in the sealing layer react with the glue provided thereover so as to yield adhesion. Accordingly, heat resistance and weather resistance are even further improved. Moreover, since the thermoplastic resin is provided in a sheet-like film, the operation time can be reduced and the factory environment control equipment can be simplified. Furthermore, in the case when a method is employed in which a primer is additionally laid between the glue and the thermoplastic resin sheet, the thermoplastic resin sheet can be securely adhered.
According to the above-described construction of the present invention, a process for producing a decorated article can be provided which has superior advantages conventional processes did not have, making it possible to prevent penetration of the glue into the overlay as the surface layer in the base material so as to provide a uniform color tone of the overlay as well as improving the heat resistance and weather resistance.